Sigh, this is what happens when people speculate outside of their field of expertise. I tried to read all of the original paper but got pissed off at their stupidity.
First off they do not understand current commercial plant breeding efforts at all. This is not surprising given that the expertise in the subject is no longer in university programs. In the 80's and 90's plant breeders could make 3-4x the money in private industry. Only the incompetent stayed behind in university programs and their students are now writing these terrible papers completely disconnected from reality.
FYI Commercial plant breeding is evolutionary processes sped up to the extreme. The companies are aggressively searching for, creating, and introgressing new traits. It's a never ending race against the constantly changing environment and other companies. In many market segments varieties only last for 4-5 years.
Pet peeve: Contrary to what idiots like this write, breeding for yield does not exist. Yield is not a trait you can select for. Yield is the end result of selecting to optimize the whole organism to match its environment: plant health, plant vigor, pest resistance, disease resistance, optimized nutrient management, soil/microbe interactions, etc. These authors are ignorant of fundamental concepts of plant breeding over 50 years old.
Finally the absolute worst thing that we should do is go back to land races. Besides causing widespread famine, all types of agriculture always damage the environment. There is no such thing as environmentally friendly farming. Going back to landraces will increase our need for agricultural land. We don't need landraces of our important food crops, we need a healthy population of evolving wild types. Using modern breeding techniques, introgressing novel new traits from wild types only take a few years.
The best way to conserve the planet is to work to restore the full ecosystems we have destroyed to farm. We need to massively reduce our land usage and rewild millions of acres. To do this we need to focus on maximizing our breeding efforts and cropping systems via protected culture and irrigation systems.